Rosali,
I've made some progress since your last posting. I downgraded to XAMPP v1.7.1. Instead of getting a blank browser window, I'm now getting a blank window the message "Service Currently Not Available: Error 500 (0x01F4)".
I downgraded down to v1.7.1 instead of v1.7.0 because I thought RoundCube would not have a problem. Did you try using XAMPP v1.7.1 with RoundCube before downgrading to v1.7.0? If not, do you have any ideas how to resolve this latest error message?
Thanks in advance for your help.
WS